Fix for @cvan's payverlay regression (bug 838186)

Removed potato-initialization of form submission handler.
Bump amo-validator

+ Added compat tests for FX19
* Cleanup of compat tests
Bump amo-validator

- Spurious debug statement
Fix for modaled filters dialog

The header is no longer underneath the modal.
unleash payments in USA
stop commit error when running celery as eager
fix filter in payments-in-USA migration